Divisionally exposing an active area in LCD with a plurality of shots

ABSTRACT

In a method of manufacturing a liquid crystal display using a divisional exposure for a substrate, an overlapping area at the boundary between adjacent shots is provided and the shots left and right to the boundary are exposed in a way that the areas of the shots gradually decreases and gradually increases, respectively, to reduce the brightness difference due to stitch errors between the two shots. For example, the number of unit stitch areas assigned to the left gradually decreases and the number of unit stitch areas assigned to the right shot gradually increases as it goes to the right along the transverse direction in the stitch area. A unit stitch includes an area obtained by dividing a pixel into at least two parts.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a method of manufacturing a liquidcrystal display (“LCD”), and in particular, to a method of manufacturingan LCD for reducing the brightness difference due to the stitch errorgenerated during manufacturing an LCD panel by divisional exposure.

(b) Description of the Related Art

Generally, for an LCD panel having an active area larger than the sizeof an exposure mask, divisional exposure dividing the active area andperforming step-and-repeat process is required for forming patterns inthe active area. That is, the active area is required to be exposedusing at least two “shots.” In practice, since the shots are subject toshift, rotation and distortion, the shots are misaligned (referred to as“stitch error” hereinafter) to generate the difference between the shotsin parasitic capacitances generated between wires and pixel electrodesand in the locations of the patterns.

The difference in parasitic capacitances and in the locations of thepatterns results in the difference in electric characteristics and inthe aperture ratios between the shots of the LCD panel, thereby causingthe difference in the brightness between the shots to appear at theboundary between the shots.

FIG. 1 is a plan view showing the boundary between shots of aconventional LCD panel.

As shown in FIG. 1, the brightness difference in adjacent shots A and Bdue to the stitch error is predominant at the boundary between the shotsand appears as a stripe.

For reducing the brightness difference, a conventional method ofmanufacturing an LCD makes the shot boundary have a saw shape as shownin FIG. 2. A plan view of two adjacent shots configured in this way isshown in FIG. 2, and the exposure areas and the brightness thereof arerespectively shown in FIGS. 8B and 9B. Although the brightnessdifference between the shots is one-step reduced at the boundary areabetween the shots as shown in the figures, the stripe is still visibleby the human eyes. Moreover, a mosaic pattern may be observed when aunit stitch area is large.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method ofmanufacturing a panel for an LCD for reducing the brightness differencebetween shots due to a stitch error when observed with the naked eyes.

To achieve the above object, an overlapping area called “stitch area” isprovided at the boundary between shots in a divisional exposure process,and the exposure areas for left and right shots gradually increases ordecreases, respectively, as goes along a transverse direction in thestitch area. At this time, a pixel is divided into more than twosubareas to be used as unit stitch areas.

The pixel area is preferably defined by intersections of two adjacentgate lines and data lines and the unit stitch area is defined by one ofareas obtained by dividing the pixel area along a division line parallelto the gate lines or the data lines.

As described above, the brightness at the boundary between shots isgradually varied by gradually changing the exposure areas between rightand left shots in a divisional exposure process, thereby making aboundary line between the shots obscure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are plan views showing two adjacent shots of aconventional LCD;

FIG. 3 is a plan view showing shots A and B of an LCD according to firstand second embodiments of the present invention;

FIG. 4 is a plan view showing a boundary area between shots of an LCDaccording to the first embodiment of the present invention;

FIG. 5 is a plan view showing a unit stitch area of an LCD according tothe first embodiment of the present invention;

FIG. 6 is a plan view showing a boundary area between shots of an LCDaccording to the second embodiment of the present invention;

FIG. 7 is a plan view showing a unit stitch area of an LCD according tothe second embodiment of the present invention;

FIGS. 8A and 8B illustrate exposure areas occupied by shot A and shot Bnear a boundary area between shots of a conventional LCD;

FIG. 8C illustrates exposure areas occupied by shot A and shot B near aboundary area between shots according to the first and the secondembodiments of the present invention;

FIGS. 9A and 9B illustrate the brightness difference between shorts of aconventional LCD; and

FIG. 9C illustrates the brightness difference between shorts accordingto the first and the second embodiment of the present invention.

FIG. 10 is a plan view showing a unit stitch area of an LCD according tothe third embodiment of the present invention;

FIG. 11 shows the number of unit stitch areas included in shot A andshot B in a boundary area between the shots A and B.

FIG. 12 shows the change of a subarea under exact alignment andmisalignment.

RESPECTIVELY DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described indetail with reference to the accompanying drawings for those skilled inthe art to easily carry out.

FIG. 3 is a plan view showing adjacent shots of an LCD panel accordingto embodiments of the present invention.

FIG. 4 is a plan view showing a boundary area between shots of an LCDaccording to the first embodiment of the present invention.

FIG. 5 is a plan view showing a unit stitch area of an LCD according tothe first embodiment of the present invention.

A stitch area is an overlapping area between two adjacent shots such asa left shot A (represented as a white area) and a light shot B(represented as a black area) as shown in FIG. 4. The stitch area isdivided into a plurality of unit stitch areas, for example, 10×9 unitstitch areas as shown in FIG. 4. The unit stitch area refers to onebasic area of the stitch area divided by n×m blocks (where n and m arenatural numbers).

In this embodiment, a pixel includes two or more unit stitch areas. Thereduced size of the unit stitch area prevents a mosaic pattern. As shownin FIG. 5, a pixel is divided into two areas a and b used as unit stitchareas according to the first embodiment of the present invention.

The unit stitch area of the first embodiment of the present inventionwill be described more in detail with reference to FIG. 5.

As shown in FIG. 5, a pixel area on a thin film transistor (“TFT”) arraypanel is defined by intersections of a plurality of gate lines 20extending in a transverse direction and a plurality of data lines 70extending in a longitudinal direction. A TFT and a pixel electrode 90having a plurality of apertures 901, 903, 905, 907, 909, 911, 913 and915 are provided in each pixel area. A common electrode (not shown)having a plurality of apertures 401, 403, 405, 407, 409, 411 and 413 isformed on a color filter panel (not shown) opposite the TFT array panel.The apertures 401, 403, 405, 407, 411, and 413 on the common electrodeare hatched. The apertures 901, 903, 905, 907, 909, 911, 913 and 915 ofthe pixel electrode 90 and the apertures 401, 403, 405, 407, 411 and 413of the common electrode are arranged in turns and partition the pixelarea into a plurality of subareas. In this case, a boundary between theareas a and b is defined by an aperture 407 of the common electrode.

According to the first embodiment of the present invention, each of thetwo areas a and b forming a pixel area is used as a unit stitch area,and the area a is exposed by shot A while the area b is exposed by shotB. In this way, since the brightness difference is much diluted comparedwith that for a case that a unit stitch area includes a pixel area, thestains such as a mosaic pattern is prevented. In addition, the aperture407 disposed at the boundary between the unit stitch areas blocks aboundary line between shots which may appear even dimly due to thebrightness difference between the unit stitch areas.

A method of manufacturing an LCD panel for reducing stitch errors inaccordance with the first embodiment of the present invention will bedescribed with reference to FIG. 4.

According to the first embodiment of the present invention, the numberof unit stitch areas for shot A in a stitch area gradually decreases andthe number of unit stitch areas for shot B in a stitch area graduallyincreases as goes to the right along the transverse direction, therebymaking the brightness in the stitch area continuously change. Here, theunit stitch areas for a shot refer to the unit stitch areas exposed bythe shot.

For example, in a stitch area including nine columns and ten rows ofunit stitch areas, the first column has nine unit stitch areas for shotA and one unit stitch area for shot B, the second column has eight unitstitch areas for shot A and two unit stitch areas for shot B, the thirdcolumn has seven unit stitch areas for shot A and three unit stitchareas for shot B, and so on. Preferably, the unit stitch areas for eachshot A or B are not gathered. It is because, if so, a macroscopic stainmay appear.

To summarize, the number of unit stitch areas for shot A graduallydecreases while the number of unit stitch areas for shot B graduallyincreases along the transverse direction.

FIG. 8C illustrates exposure areas for shot A and shot B and a stitcharea along the transverse direction. As shown in FIG. 8C, since thenumber of unit stitch areas for shot A and that of shot B decreases andincreases, respectively, along the transverse direction in the firstembodiment of the present invention, the brightness difference betweenthe shots A and B gradually changes.

FIG. 9C illustrates the brightness of adjacent shorts and a stitch areatherebetween of an LCD panel according to the first embodiment of thepresent invention.

The horizontal axis shown in FIG. 9C indicates shot A, a stitch area,and shot B along an increasing direction, and the vertical axis shown inFIG. 9C indicates brightness. In this graph, which shows the brightnessin the stitch area when shot A is brighter than shot B, the stitch areabecomes gradually darker as it goes from area A to area B.

FIG. 6 is a plan view showing the boundary area between shots of an LCDaccording to a second embodiment of the present invention, and FIG. 7 isa plan view showing unit stitch areas of an LCD according to the secondembodiment of the present invention.

As shown in FIG. 6, the second embodiment of the present inventionarranges the shots such that the exposure area for shot A in each unitstitch area gradually decreases in the stitch area while the exposurearea for shot B in the unit stitch area gradually increases as goes tothe right along the transverse direction in the stitch area. As aresult, the brightness in the stitch area gradually changes.

For example, in a stitch area including nine columns and ten rows ofunit stitch areas, each unit stitch area of the first column assigns its90% area to shot A and its 10% area to shot B, each unit stitch area ofthe second column assigns its 80% area to shot A and its 20% area toshot B, each unit stitch area of the third column assigns its 70% areato shot A and its 30% area to shot B, and so on.

To summarize, an area in a unit stitch area assigned to shot A graduallydecreases while an area of the unit stitch area assigned to shot Bgradually increases along the transverse direction.

This arrangement gradually varies the brightness between the unit stitchareas for the shots A and B along the transverse direction.

In this embodiment, a pixel includes two or more unit stitch areas. Thereduced size of the unit stitch area prevents a mosaic pattern. As shownin FIG. 7, a pixel is divided into four areas a, b, c and d used as unitstitch areas according to a second embodiment of the present invention.

Now, the unit stitch areas according to the second embodiment of thepresent invention will be described more in detail with reference toFIG. 7.

As shown in FIG. 7, a pixel area on a TFT array panel is defined byintersections of a plurality of gate lines 20 extending in a transversedirection and a plurality of data lines 70 extending in a longitudinaldirection. A TFT and a pixel electrode 90 having a plurality ofapertures 901, 903, 905, 907, 909, 911, and 913 are provided in eachpixel area. A common electrode (not shown) having a plurality ofapertures 401, 403, 405, 407, 409, 411 and 413 is formed on a colorfilter panel (not shown) opposite the TFT array panel. The apertures401, 403, 405, 407, 411, and 413 on the common electrode are hatched.The apertures 901, 903, 905, 907, 909 and 911 of the pixel electrode 90and the apertures 401, 403, 405, 407, 411 and 413 of the commonelectrode are arranged in turns and partition the pixel area into aplurality of subareas. The arrangements of the apertures in the areas aand b are symmetrical with respect to their boundary, the arrangementsof the apertures in the areas b and c are symmetrical with respect totheir boundary, and the arrangements of the apertures in the areas c andd are symmetrical with respect to their boundary. The boundaries betweenthe areas a, b, c and d are defined by the apertures 401, 403, 405, 407,409, 411, 413 of the pixel electrode and the apertures 901, 903, 905,907, 909, and 911 of the common electrode. In this embodiment, althoughthe apertures are exemplified as subarea-dividing members, a pluralityof protrusions or depressions may also be used as subarea-dividingmembers.

According to the second embodiment of the present invention, each of thefour areas a, b, c and d forming a pixel area is used as a unit stitcharea, and exposed by one of shot A and shot B. Exemplary combinations ofareas for shot A and shot B are (a; b, c and d), (a and b; c and d), (a,b and c; d), and (a and d; b and c). In this way, since the brightnessdifference is much diluted compared with that for a case that a unitstitch area includes a pixel area, the stains such as a mosaic patternis prevented. In addition, the apertures 401, 403, 405, 407, 409, 411,413, 901, 903, 905, 907, 909, 911 disposed at the boundary between theunit stitch areas block boundary lines between shots which may appeareven dimly due to the brightness difference between the unit stitchareas.

The exposure areas and the brightness of the adjacent shots according tothe second embodiment of the present invention are illustrated in FIGS.8C and 9C, respectively. The descriptions about FIGS. 8C and 9Caccording to the second embodiment are substantially the same as thataccording to the first embodiment.

FIG. 10 is a plan view showing a unit stitch area of an LCD according tothe third embodiment of the present invention.

As shown in FIG. 10, a pixel area on a tin film transistor array panelis defined by intersections of a plurality of gate lines 20 extending ina transverse direction and a plurality of data lines 70 extending in alongitudinal direction. A TFT and a pixel electrode 90 having aplurality of apertures 901, 903, 905, 907, 909, 911, 913 and 915 areprovided in each pixel area. A common electrode (not shown) having aplurality of apertures 401, 403, 405, 407, 409, 411, 413 and 415 isformed on a color filter panel (not shown) opposite the TFT array panel.The apertures 401, 403, 405, 407, 411, 413 and 415 on the commonelectrode are hatched. The apertures 901, 903, 905, 907, 909, 911, 913and 915 of the pixel electrode 90 and the apertures 401, 403, 405, 407,411, 413 and 415 of the common electrode are arranged in turns andpartition the pixel area into a plurality of subareas. In thisembodiment, although the apertures are exemplified as subarea-dividingmembers, a plurality of protrusions or depressions may also be used assubarea-dividing members.

In this embodiment, a pixel area includes sixteen unit stitch areas. InFIG. 10, area a represents a unit stitch area.

According to the third embodiment of the present invention, each of thesixteen areas forming a pixel area is used as a unit stitch area andexposed by different shot. In this way, since the brightness differenceis much diluted compared with that for cases that a unit stitch areaincludes an area obtained by dividing a pixel area along a transversedirection according to the first and second embodiments of the presentinvention, the stains such as a mosaic pattern is prevented.

In the third embodiment, the unit stitch area includes one ofequally-divided sixteen areas of one pixel area. However, the number ofthe division of one pixel for defining the unit stitch area may belarger than or smaller than sixteen.

A distinctive feature of the third embodiment of the present inventiondistinguished from the second embodiment is that the division of onepixel for defining the unit stitch area is performed along thelongitudinal direction as well as the transverse direction.

FIG. 11 shows the number of unit stitch areas included in shot A andshot B in a boundary area between the shots A and B when an LCD ismanufactured according to the third embodiment of the present invention.In FIG. 11, white color represents the areas of shot A and black colorrepresents the areas of shot B. Also, boundaries indicated by arrowsrepresent boundaries between pixel areas.

As shown in FIG. 11, the number of the unit stitch areas of shot B issix in the leftmost pixel area, while the number of the unit stitchareas of shot B is one in the rightmost pixel area. The number of theunit stitch areas of shot B deceases as it goes to the right. Toconsider the areas not shown in the figure, all unit stitch areas arethose of shot B since the number of the unit stitch areas of shot Bincreases as it goes to the left. Similarly, all unit stitch areas arethose of shot A since the number of the unit stitch areas of shot Bdeceases while that of shot A increase as goes to the right.

Therefore, even if misalignment occurs, the width of a subarea offsetfrom an expected value predominantly decreases compared with aconventional art. This will be described with reference to FIG. 12.

FIG. 12 shows the change of a subarea under exact alignment andmisalignment. In FIG. 12, a figure represented as “exact alignment” isan expected subarea, and a figure represented by “misalignment” is anincreased subarea due to the misalignment.

Upon misalignment, the increment takes only a portion of the totallength in the embodiment of the present invention, while the incrementtake all portions of the total length according to a conventional art.Therefore, according to the present invention, the width of a subareaoffset from an expected value under misalignment considerably decreasescompared with a conventional art.

Meanwhile, a plurality of photolithography steps, that is, a pluralityof exposures for a plurality of layers are required for forming wires,pixel electrodes, and switching elements of an LCD, especially of anactive matrix type LCD (“AMLCD”). In this case, it is required to alignthe stitch area and the unit stitch areas in the exposure process of theplurality of layers for gradually changing the brightness with accuracy.In addition, stitch areas or unit stitch areas may be differed or thestitch areas for a specific layer(s) may have linear or saw shapes.

As described above, the brightness difference due to stitch errors in anLCD panel is reduced by gradually changing the exposure areas betweenright and left shots in a divisional exposure process of the LCD panel.

1. A method of manufacturing a liquid crystal display by divisionallyexposing an active area with a plurality of shots including first andsecond shots adjacent to each other, the method comprising: preparing astitch area which is an overlapping area of the first and the secondshots at a boundary between the first shot and the second shot; andperforming gradual decrease of an area for the first shot and gradualincrease of an area for the second shot in the stitch area along adirection from the first shot to the second shot, wherein the decreaseof an area for the first shot and the increase of an area for the secondshot are preformed by unit of a unit stitch area obtained by dividing apixel area into at least two parts, a subarea-dividing member isprovided in a pixel area, and the subarea-dividing member is located ata boundary between the unit stitch areas, the subarea-dividing memberbeing defined by at least one of a pixel electrode and a commonelectrode.
 2. The method of claim 1, wherein the pixel area is definedby intersections of two adjacent gate lines and data lines and the unitstitch area is defined by one of areas obtained by dividing the pixelarea along a division line substantially parallel to the gate lines. 3.The method of claim 2, wherein the pixel area is defined byintersections of two adjacent gate lines and data lines and the unitstitch area is defined by one of areas obtained by dividing the pixelarea along a division line substantially parallel to the data lines. 4.The method of claim 1, wherein the pixel area is defined byintersections of two adjacent gate lines and data lines and the unitstitch area is defined by one of areas obtained by dividing the pixelarea along a division line substantially parallel to the data lines. 5.The method of claim 1, wherein the subarea-dividing member is one of anaperture, a protrusion, and a depression.
 6. The method of claim 1,wherein the subarea-dividing member is formed in at least one of Thepixel electrode and the common electrode.
 7. A method of manufacturing aliquid crystal display by divisionally exposing an active area with aplurality of shots including first and second shots adjacent to eachother, the method comprising: preparing a stitch area which is anoverlapping area of the first and the second shots at a boundary betweenthe first shot and the second shot; and performing gradual decrease ofan area for the first shot and gradual increase of an area for thesecond shot in the stitch area along a direction from the first shot tothe second shot, wherein the decrease of an area for the first shot andthe increase of an area for the second shot are preformed by unit of aunit stitch area obtained by dividing a pixel area into at least twoparts, a subarea-dividing member is provided in a pixel area, and thesubarea-dividing member is located at a boundary between the unit stitchareas, and wherein the pixel area is defined by intersections of twoadjacent gate lines and data lines and the unit stitch area is definedby one of areas obtained by dividing the pixel area along a divisionline substantially parallel to the gate lines and along a division linesubstantially parallel to the data lines.